Tobacco materials used in making reconstituted tobacco sheets, whether using all-tobacco or using tobacco plus binders, require grinding or refining as parts of their preparation for use in the manufacturing process. Refining includes cutting, disturbing the fibrous arrangement, and otherwise working, sizing and preparing the tobacco material for use as a part of the slurry to be extruded on a wire or screen or, alternatively, cast to form a film or sheet.
Prior methods of making reconstituted sheets have described the amount or degree of refinement in terms of pulp freeness or particle size. For example, U.S. Pat. No. 3,464,422 describes a method of refining a slurry of tobacco stock to a Schopper-Riegler value of -100 millimeters (ml); U.S. Gooijer U.S. Pat. No. 3,097,653 refines the tobacco by grinding it until 30% is retained on a 100 mesh sieve and 99% passes through an 18 mesh sieve; Osborne U.S. Pat. No. 3,125,098 discloses a process in which refinement is defined by inverted or negative freeness as measured by the Canadian Standard Freeness (CSF) test and finally Domeck U.S. Pat. No. 3,115,882 uses a Clark Classifer screen to measure the degree of wet grinding.